FIG. 6 is a schematic configuration diagram of a general, conventional power supply system of a data center with a plurality of loading devices such as a plurality of servers that use DC voltage as the driving power supply. This power supply system has an uninterruptible power supply apparatus (UPS) 1 interposed in a 400 V system power supply, and an AC power distributor (PDU) 2 for converting high-voltage AC power (AC 400 V), supplied through the uninterruptible power supply apparatus 1, into, for example, 200 V or 100 V AC power.
The uninterruptible power supply apparatus 1 basically has a high-capacity battery (BAT) 1a capable of storing DC power. The uninterruptible power supply apparatus 1 is also configured by an AC/DC converter 1b for converting the high-voltage AC power to a DC voltage to charge the battery 1a, and a DC/AC converter 1c for converting the output voltage of the AC/DC converter 1b or the DC power stored in the battery 1a to high-voltage AC power and outputting the high-voltage AC power.
The power distributor 2 has, for example, a breaker 2a for separating the system power supply from a load system having the loading devices (servers). The AC power distributor 2 further has a transformer 2b for converting the high-voltage AC power (AC 400 V) to, for example, 200 V AC power and outputting the 200 V AC power. Note that reference numeral 3 shown in the diagram represents a transformer that converts AC power, which is distributed at, for example, 6.6 kV, into the high-voltage AC power (AC 400 V), and brings the high-voltage AC power into a building provided with the uninterruptible power supply apparatus 1 and the like.
The load system, constructed by the plurality of servers 4 serving as the loading devices, has, in front thereof, a switching power supply 5 that is connected to the power distributor 2 and generates low-voltage DC power of 48 V or lower (e.g., DC 12 V) from the AC power (AC 200 V) to drive the servers 4. This switching power supply 5 generally has an AC/DC converter 5a for converting the AC power (AC 200 V) into a DC voltage, and a DC/DC converter 5b for converting the output voltage of the AC/DC converter 5a into a DC output voltage (DC 12 V) to be supplied to the servers 4. The plurality of servers 4 are connected to the switching power supply 5 and operated by supply of the DC output voltage from the switching power supply 5, the DC output voltage being the driving power supply for the servers 4 (see Patent Document 1, for example).
The plurality of servers 4 are usually configured such that a certain number of servers 4 are stored in a server rack as a group of servers, and the switching power supply 5 is provided for each group of servers. The switching power supply 5 is stored in the server rack together with the certain number of servers 4. These servers 4 construct a so-called “multinode server.”
Examples of the technique related to the uninterruptible power supply apparatus 1 of the foregoing power supply system include a technique disclosed in, for example, Patent Document 2 in which uninterruptible power supply apparatuses are run parallel. Patent Document 3 discloses a technique in which, when the number of uninterruptible power supply apparatuses to be run parallel are increased, the capacities of the batteries are changed by changing over the switches to connect only the batteries in parallel.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-143104
Patent Document 2: Japanese Unexamined Patent Application Publication H7-184322
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2006-230029